To meet increasingly stringent fuel economy and provide impetus to develop powertrain controls that use specific humidity as an input on some vehicles to control engine operating parameters such as air-fuel ratio, exhaust gas recirculation rate, etc. As the specific humidity affects aircharge density, universal gas constant, ratio of specific heats and oxygen content among other things, accurate specific humidity data is used in calculation of EGR rates, spark timing, and control of air-fuel ratio and other powertrain controls. Incorporating specific humidity into calculations for such parameters has previously involved a humidity sensor on a vehicle. Development of a sensor to measure specific humidity in a vehicle is difficult because such devices use precise measurement of specific heat or air density. Further, some of the water in the air is not in the form of vapor, but as an aerosol which further complicates humidity measurement. As this is rarely feasible in a moving vehicle a relative humidity device has been used that estimates specific humidity from the relative humidity, the ambient temperature and the ambient pressure.
Estimating the specific humidity based on relative humidity results in a loss of accuracy because estimation of the saturation specific humidity is inaccurate and depends on factors such as the presence of ice and water in the surface environment and the size and chemistry of aerosol particles in the air among other factors. Furthermore, relative humidity sensors are expensive and temperamental. Without calibration, the accuracy of relative humidity sensors may be drastically reduced. Due to the variable nature of direct humidity sensors, use of additional, humidity sensors or additional, paired weather sensors may be necessary.
The inventors herein recognize the aforementioned difficulties and associated costs of a physical humidity sensor or other weather sensors and disclose systems and methods for deriving the specific humidity from sensor data readily available on the vehicle bus. A virtual humidity sensor is disclosed that accepts inputs from the vehicle position/time/date sensor, an ambient temperature sensor, a barometric pressure sensor, and other data normally available on the vehicle bus such as windshield wiper status, pyrometer measurements, fuel density, etc. External data from a wireless device, if it is available, may be used to increase the accuracy of the calculation. Wireless devices like IBOC (in-band on-channel, e.g. HD Radio) and Satellite radios are now installed on most vehicles these devices may receive data collected from weather stations and broadcast by local radio stations.
The disclosed sensor may be an informational filter implemented in software and run on a computer embedded on the vehicle and connected to the vehicle (CAN) bus. The filter will be implemented as a learning algorithm such as a neural network that is first trained offline using historical weather and other data, and then later can be trained online (in the vehicle) with external data when it is available.
Systems and methods are provided for adjusting an engine powertrain component responsive to ambient humidity, the ambient humidity based on vehicle position in a region, ambient temperature, and historical humidity data for that region for a current time of year and the time of the day. This may be accomplished without relying on a costly, and often, temperamental physical humidity sensor. Training modules and cloud updates further increase the accuracy of the virtual humidity sensor of the present disclosure.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Further, the inventors herein have recognized the disadvantages noted herein, and do not admit them as known.